Control broadcast programme signal, control write and read systems, related production and broadcasting channel

ABSTRACT

The invention relates to programs enhanced by applications. It relates, furthermore, to the associated production and broadcasting systems, in particular to interactive digital television. The activation of an interactive application associated with a broadcast program may be done manually in the broadcasting channel. This solution is expensive, lacks accuracy, and the control of the application is managed not by the production channel but the broadcasting channel. The invention therefore proposes to use a broadcasting program signal comprising primary data for the reproduction of the passive main content of the program and secondary data watermarked in the primary data. These secondary data comprise the commands for triggering at least one application such as, in particular, the controlling of one or more broadcasting parameters of said program signal and/or of one or more applications, for example interactive or broadcasting, related to said program signal.

The invention relates to programs enhanced by applications, inparticular by interactive applications and/or broadcasting applications.It relates, furthermore, to the associated production and broadcastingsystems, in particular to interactive digital television.

Interactive televised programs exist today but have said interactivecontent as their sole content. For example, home banking, weather orcooking channels, etc. These are programs dedicated to an interactive|content, this interactive content occupying the entire screen. Theprogram being totally dedicated to the interactive content, it is easyto limit its use to subscribers alone through encryption for example.The encryption key is then provided to the subscribers under specifiedconditions, payment of a subscription for example. These programs havingonly interactive content therefore make it possible to target theirusers.

More generally, interactive television consists in enhancing traditionaltelevision, that is to say the passive viewing of a video program,through contextual applications, known as “enhanced TV”. The backgroundof the screen therefore remains occupied by the video program to whichinformation is added by way of the decoder. This information allows theuser to interact by virtue of the remote control of the decoder. Theinteractivity then pertains to a predefined video sequence or even to asingle video image.

For example, during televised games, the viewer himself can also respondto questions at the same time as the candidates with the possibility ofwinning prizes. Another example is to allow the viewer to vote livewithout having to pick up their telephone by simply pressing one of thebuttons of their remote control (such as for electing Miss, singer,etc.). Interactive television can also be beneficial in respect oftelepurchase transmissions, making it possible, for example, at anymoment during the transmission to put into a virtual basket or to removetherefrom the objects that one wishes to order and then to place theorder, all of this by simply pressing the buttons of one's remotecontrol while not budging from in front of one's television set.Interactive advertisements can also be envisaged, offering samples or atrial of the object of the advertisement. Or else games on which theviewer can bet like horse racing, etc.

The use of the remote control as interaction interface simplifies theimplementation of interactivity for the viewer and reduces the costssince it is not necessary to purchase a particular interface, telephone,Internet connection, suitable infrared keyboard etc. for example.

FIG. 1 diagrammatically shows the production and broadcasting channelsfor a video program according to the prior art. The production channel100 makes it possible to obtain a video program stored on a cassette 150sent to the broadcasting channel 200. This may for example be aprofessional video cassette containing the video program to be broadcastand commonly called the RTB, that is to say ready to broadcast. This RTBcassette 150 is then read by the video cassette reader VTR 211 of thebroadcasting channel 200 (VTR is the abbreviation standing for VideoTape Reader). The video program is then coded by the video coder 231, itgenerally being an MPEG coder 2.

The multiplexer 240 receives several types of data. It processes thecoded video program generated by the video coder 231. But also, forexample, IP/MEPG data emanating from a server 233 are presented onanother input of the multiplexer 240. They may for example cater for anInternet connection. The output of an EPG generator 233 (EPG is theabbreviation standing for electronic program guide) can be coupled toone of the inputs of the multiplexer 240. To cater for VOD video ondemand services or NVOD near video on demand services, the signalsgenerated by the device 234 are received by the multiplexer 240. Forvarious reasons, it may be desirable to limit the access to certainprograms. These reasons may be moral: programs intended for certainpopulation brackets (adults, for example) or more simply financial:creation of profits on certain programs, etc. A device 236 thengenerates conditional access data associated with these programs, suchas for example an encryption key. The multiplexer can also receiveinteractive data generated by the module 237 (for example, forinteractive channels such as the weather channel, etc).

As far as the video programs enhanced by interactive applications areconcerned, the interactive applications broadcasting device 235 willsearch for the interactive application to be broadcast during a period Tin a server 215 and transmit it to the multiplexer 240.

The multiplexer 240 transmits all of these data after processing, inparticular segmentation for packet transmission, to the modulator 250for their broadcasting with the aid of at least one transmitting antenna260.

It is conceivable to broadcast an interactive application over largetimeslots thereby ensuring that the application is broadcast during itsactivation. However, the larger the timeslot for broadcasting theinteractive applications, the more the bandwidth is occupied. Now, thisbandwidth is limited, and therefore broadcasting over large timeslotslimits the number of interactive applications broadcast simultaneously.

In the case of interactive applications synchronized with the videoprogram, additional constraints have to be taken into account. Theactivation of an interactive application reprograms the user's decoderto receive his reaction (programming of the button(s) of the remotecontrol for this interactive application) and possibly upload thisreaction to the broadcaster 200. The activation of the interactiveapplication may then be done manually by the intervention of an operatorO at the level of the interactive applications broadcasting device 235.The device 235 for broadcasting interactive applications upon theintervention of the operator O transmits the command for triggering theactivation of the interactive application identified by this command tothe multiplexer 240. The operator O views the video program broadcastand manually triggers the activation of the interactive application viathe interactive applications broadcasting device 235. The cost of theinteractivity of the program is necessarily high on account of the useof an operator O. Moreover, an operator O is inaccurate, this being adrawback for interactive applications related to a single video image orto very short video sequences.

Another problem is that the production channel 100 normally loaded withthe content of the programs does not manage the interactive content ofthe program in question but only its video content. The commands fortriggering the broadcasting and the activation of an interactiveapplication of the program are managed by the operator O of thebroadcasting channel 200.

Should the video program be stored on a professional video cassette 150,a solution proposed in this case consists in writing the commands (knownas triggers) for triggering at least the activation of the interactiveapplications in the video related data areas. In this case, both thevideo and the interactive content are managed by the production channel100. Specifically, the production channel 100 provides the broadcastingchannel 200 with a RTB cassette 150 on which is written the globalcontent of the program: both the video and the instants of triggering ofthe interactive applications. However, the equipment handling the RTBcassettes 150 before broadcasting spoils the video related data area.Consequently, the triggering commands are deleted, at least in part.These techniques are therefore neither generic nor deployable since theyare unreliable on account of the loss of triggering commands.

The present invention makes it possible to obviate these drawbacks byproposing to write commands for triggering applications intended for thebroadcasting channel. In particular, these commands may be commands fortriggering the interactive application in the program signal itself, forexample, the video signal. In this way the data related to theapplication (interactive, broadcasting, etc) cannot be separated fromthe main content of the program, in particular the video. Hence,whatever the operations carried out on the program signal, in particularon the RTB cassette 150, the commands for triggering the applicationwill survive. This makes it possible, in terms of utilization, to affordtechnical guarantees that the interactive program will be broadcastcorrectly, and then reproduced.

The invention therefore relates to a broadcasting program signalcomprising primary data for the reproduction of the passive main contentof the program, which comprises secondary data watermarked in theprimary data. The secondary data do not alter the reproduction of themain content of the primary data.

These secondary data comprise the commands for triggering at least oneapplication related to the main content of the primary data.

These secondary data make it possible to control the triggering ofapplications such as, in particular, the controlling of one or morebroadcasting parameters of said program signal and/or of one or moreapplications related to said program signal.

Furthermore, the secondary data allow, for example, the triggering ofthe broadcasting and/or of the activation of at least one interactiveapplication related to the main content of the primary data.

Another subject of the invention is a system for writing commandswriting secondary data, allowing the triggering of at least oneapplication, in a program signal comprising at least primary data forthe reproduction of the passive main content of the program. Thiscommand writing system comprises:

-   -   a first input e₁ receiving primary data for the reproduction of        the passive main content of the program,    -   a second input e₂ receiving predetermined control criteria,    -   a reproduction and editing device 160 coupled to these first and        second inputs e₁ and e₂, said device 160 reproducing the main        content of the primary data, which content is received on the        first input e₁, and editing on its output at least one secondary        datum making it possible to control the triggering of at least        one application related to the main content of the primary data,        which application is reproduced at this instant according to the        predetermined interactivity criteria received on this second        input e₂,    -   a watermarking device 170 receiving the primary data of the        first input e₁ and secondary data, and generating a program        signal comprising the primary data and the secondary data        watermarked in the primary data, said watermarking not altering        the reproduction of the main content of the primary data,    -   an output coupled to the output of the watermarking device 170.

In particular, the predetermined control criteria may be predeterminedinteractivity criteria, and said reproduction and editing device 160 canedit on its output at least one secondary datum making it possible tocontrol the triggering of the broadcasting and/or of the activation ofat least one interactive application related to the main content of theprimary data, which application is reproduced at this instant accordingto said predetermined interactivity criteria received on this secondinput e₂.

The invention furthermore proposes a production channel comprising inseries a system for producing a program signal comprising primary datafor the reproduction of the passive main content of the program and acommand writing system as described hereinabove.

The invention also relates to a system for reading a command in aprogram signal comprising primary data for the reproduction of thepassive main content of the program and at least one secondary datumwatermarked in the primary data. This command reading system 220comprises:

-   -   a first input receiving the program signal,    -   a watermark reading device 221, reading the secondary data        watermarked in the primary data, these secondary data comprises        commands for triggering at least one application related to the        main content of the primary data,    -   an output receiving triggering commands.

The secondary data transmitted on the output of the command readingsystem 220 may, furthermore, comprise synchronized commands such as fortriggering the activation and/or the broadcasting of the interactiveapplications identified by the triggering commands is synchronized withthe reproduction of the primary data in which the secondary dataassociated with these triggering commands are watermarked.

Optionally, the command reading system comprises a synchronizationdevice 225 receiving at least the secondary data and generating saidsynchronized triggering commands.

According to the invention, a program broadcasting channel is proposed.It comprises several devices, including at least:

-   -   a device 221 for reading a program signal comprising primary        data for the reproduction of the passive main content of the        program and at least one secondary datum watermarked in the        primary data,    -   a program signal coder 231 coupled to the output of said program        signal reading device 221,    -   a command reading system 220 as claimed in one of claims 7 or 8        coupled to the output of said program signal reading device 211        and/or to the output of said program signal coder 231 and to the        input of at least any one of the devices of said broadcasting        channel, the triggering commands generated by the command        reading system 220 controlling said device of said broadcasting        channel, which device is coupled to said command reading system        220,    -   and/or an interactive applications server 215, a device for        broadcasting interactive applications 235 coupled to said        interactive applications server 215,    -   a multiplexer 240 coupled at least to the outputs of the program        signal coder 231 and to the interactive applications        broadcasting device 235.

Optionally, said command reading system 220 is coupled to saidinteractive applications broadcasting device 235, the triggeringcommands generated by the command reading system 220 controlling thetransmission of the interactive applications originating from saidinteractive applications server 215 to the multiplexer 240 and/or thetransmission to the multiplexer 240 of the order for activation of oneor more interactive applications identified by these triggeringcommands.

The characteristics and advantages of the invention will become moreclearly apparent on reading the description, given by way of example,and of the figures pertaining thereto which represent:

FIG. 1, a partial diagram of the production and broadcasting channelsfor video programs with interactive applications according to the priorart,

FIG. 2, a partial diagram of the production channel for video programswith interactive applications according to the invention,

FIG. 3, a partial diagram of the broadcasting channel for video programswith interactive applications according to the invention,

FIG. 4, a diagram of the reading system according to the invention,

FIGS. 5 a and 5 b, diagrammatic representations of the progress of animage and of the associated interactive application in the broadcastingchannel according to the invention, FIG. 5 a corresponding to the use ofan interactive system supporting the dispatching of explicitsynchronization messages relating to the time base of the primary signal(in particular the MHP standard) and FIG. 5 b corresponding to aninteractive system for which the controlling of the activation of aninteractive application can be done only by managing its instant ofbroadcasting in the signal received by the decoder (in particular thesystems of OpenTV or MediaHighway type),

FIG. 6, a general partial diagram of the broadcasting channel for videoprograms with commands triggering various applications according to theinvention.

The watermarking of primary data for the reproduction of the passivemain content of the program by secondary data allowing the triggering ofthe broadcasting and/or of the activation of at least one interactiveapplication related to the main content of the primary data implementstwo devices:

-   -   one responsible for writing the secondary data into the primary        data sequence,    -   the other capable of detecting and of reading secondary data in        a primary data signal.

In the command writing system envisaged by the invention, thewatermarking device 170 is situated in the production channel 100* andcoupled to a reproduction and editing device 160 from which it willreceive the secondary data to be watermarked in the primary data, as isrepresented in FIG. 2.

The watermarked reading device 221 is situated in the broadcastingchannel 200* as shown by FIG. 3. It is connected to a device 211 forreading the interactive program signal on the storage medium 180. Thewatermark reading device 221 controls, for example, the device forbroadcasting the interactive applications 235.

FIG. 2 shows the part of the program production channel 100* dedicatedto the installing of the means required to control the triggering of theapplications, in particular to interactivity, according to theinvention. The program signal comprising the primary data of the passivemain content of the program are, for example, stored on a professionalvideo cassette 150, in particular according to the CCIR 601 standard.

The reproduction and editing device 160 receives this program signal onits first input e₁. It reproduces the main content of the program on thebasis of these primary data. Hence, if the main content of the programis visual, it displays the video image sequence. If it is an audioprogram, it broadcasts the sound sequence.

Control criteria which are, for example, interactivity criteria arereceived on a second input e₂ of this reproduction and editing device160. These criteria may be various. The interactivity criteria aredivided into two categories: one associated with the broadcasting of theinteractive applications, the other with their activation. Thesecriteria may comprise methods such as, for example, the calculation ofthe broadcasting slot of an interactive application as a function of theslot or of the instant of its activation (for example, beginning thebroadcasting of the interactive application 5 s after its activation andhalting its broadcasting 5 s after its activation), or else associatethe activation of an interactive application with a sequence comprisinga predetermined object (by recognition of the object in the contentreproduced—recognition of an image or of sound—). The reproduction andediting device 160 then identifies the sequence with which must beassociated using the method advocated.

These control criteria may also be fixed manually by an operator O* byvirtue of an interface whose output is coupled to the input e₂ of thereproduction and editing device. Even if, here again, an operator isused, he intervenes only once. Whereas today, for a program stemmingfrom a single production channel 100, if this program is broadcast byseveral broadcasting channels 200 or several times by one and the samebroadcasting channel 200, the intervention of an operator O is necessaryon each broadcasting channel 200 and is so for each broadcast. Hence,the global production cost is decreased by the intervention of a singleoperator O*.

Moreover, owing to the numerous interventions, not only is there aproblem of inaccuracy as to the instant of activation of the applicationof interactive type with respect to the main content but moreover itwill not be the same with each reproduction of the interactive program.Whereas a single operator O* intervening in the production channel 100*can, with the aid of the reproduction and editing device 160, view inthe case of a video content, listen in the case of a sound content, etc.at different speeds or even image (video or sound, etc.) by image so asto obtain better accuracy in the associating of a given interactiveapplication with a sequence or an image of the main content of theprimary data.

The reproduction and editing device 160 then edits secondary data thatare application triggering commands, in particular commands fortriggering the broadcasting and/or activation of the interactiveapplication associated with the image or the image sequence reproduced.The secondary data allowing the triggering comprises the index of theinteractive application, and optionally a code making it possible todetermine whether one is dealing with a command for triggeringbroadcasting (start or end of broadcasting) or activation if both typesof information are produced.

There may therefore exist four types of secondary data for triggering aninteractive application. The first intended for the activation of theinteractive application and which are watermarked in the primary datasequences whose passive main content will be supplemented by theinteractive application in question. The second intended for startingthe broadcasting of the interactive application at the instant ofbroadcasting of the image primary data in which this secondary datum iswatermarked. The third intended for stopping the broadcasting of theinteractive application at the instant of broadcasting of the imageprimary data in which this secondary datum is watermarked. Moreover, afourth type of secondary data may be envisaged. This is asynchronization message making it possible to identify the start of avideo sequence. This message allows the reading device (211, 220) tocalculate the temporal parameters necessary for the synchronization ofthe secondary data with the primary data.

The use of the second and third type of secondary data makes it possibleto automate the process for broadcasting the interactive applications.Thus, bandwidth is saved. This is not the case today with the use ofscheduling of timeslots for broadcasting interactive applications donemanually. Manual configuration is a source of error and uses veryconsiderable margins on the broadcasting period—several hours—givingrise to a loss of bandwidth.

Moreover, an identifier of the broadcaster for which the secondary dataare intended may be envisaged, in particular for those data concerningthe triggering of the broadcasting of the interactive application. Thus,a different broadcasting slot may be calculated according to thetechnical characteristics of each broadcasting channel 200*. Thereproduction and editing device 160 then formulates different secondarydata depending on the destination broadcasting channel 200*.

The secondary data edited by this reproduction and editing device 160are transmitted to a watermarking device 170 (known as a watermarkembedder). This watermarking device 170 furthermore receives the primarydata of the program signal, which is for example stored on the RTB videocassette 150. The interactive program signal obtained at the output ofthe watermarking device 170 comprises the secondary data watermarked inthe primary data.

This watermarking does not alter the reproduction of the passive maincontent of the primary data. This signifies, in particular in the caseof a video passive main content, that the viewer cannot see thedifference between the video image before and after watermarking. In thesame way, the watermarking of a sound sequence should not be audible tothe person listening to the interactive program.

For the watermarking of secondary data in video primary data, it isconceivable to call upon the method and device described by patentapplication WO 0065840. However, in general, any existing image or soundwatermarking device or method may be implemented by this watermarkingdevice 170.

The interactive program signal thus obtained by the watermarking device170 is stored on a medium 180 which may again be a professional videocassette RTB.

The existing methods of image watermarking permitting the watermarkingof words of different length of up to 64 bits, a secondary datum may bea word of up to 64 bits. However, the lighter (small number of bits) theword making up the secondary datum, the more robust this secondary datumwould be. Specifically, this makes it possible, for example to write thesecondary datum into a single image (video, sound, etc) several times orto write the secondary datum after coding by an error correcting code.

Let us take, for example, the case of secondary data composed of 32-bitwords. A 32-bit secondary datum may then comprise 4 bits coding the typeof triggering, optionally 4 bits identifying the destinationbroadcasting channel, 16 bits allowing identification of the interactiveapplication, for example through its index in an interactive applicationserver. This index follows, for example, the format specified by thestandard used, in particular the MHP standard. The other 8 bits make itpossible to reference an event in particular within the giveninteractive application.

FIG. 3 shows the part of the broadcasting channel 200* for the exampleof interactive program broadcasting dedicated to the installing of themeans necessary for the control of triggering of an application such asinteractivity according to the invention.

A reading device 211 for the storage medium 180 reads the program signalcomprising the primary data and the watermarked secondary data. Ittransmits this signal to a primary datum coder 231, an audio coder ifthe primary data are audio, a video coder if they are video, etc.Furthermore, it transmits said program signal to a command readingsystem 220.

This command reading system 220 is capable of reading the secondary datawatermarked in the primary data and of creating an order for controllingthe device for broadcasting the interactive applications 235. Thisinteractive application broadcasting device 235 transmitting to themultiplexer 240 upon an order from the command reading system 220 theinteractive application to be broadcast that it will have searched forin the interactive applications server 215 and/or this application'sactivation order intended for the end user's decoder.

The order compiled by the command reading system 220 comprises theinteractive application's identifier given by the secondary datum. Inthe case of a secondary datum for the triggering of broadcasting, itcomprises a command intended for the interactive applicationbroadcasting device 235 to start or stop the transmission of theidentified interactive application from the interactive applicationserver 215 to the multiplexer 240. In the case of a secondary datum forthe triggering of activation, it comprises a command intended for theend user's decoder that the interactive application broadcasting device235 transmits to the multiplexer 240. It is conceivable for the commandsgenerated by the command reading system 220 to comprise information suchthat they are executable only by a single interactive applicationbroadcasting device 235. This signifies that these devices 235 areidentified by a unique value, so that there is selective processing ofthe broadcasting or activation commands. In this case, said interactiveapplication broadcasting device 235 retranscribes only the commandsintended for the decoder of the end user addressable by the broadcastingsignal.

In all cases, the triggering commands generated by the command readingsystem 220 are synchronized with the image (sound, video, etc.) or theimage sequence formed by the primary data and in which the secondarytriggering data from which said command originated were watermarked.This synchronization is performed so that the broadcasting and/or theactivation of the interactive application identified by the secondarydatum is synchronized with the reproduction of the passive main contentof the primary data, in which the secondary datum is watermarked.

In the example of FIG. 3, the command reading system 220 has two inputs,one coupled directly to the output of the program signal reading device211, the other to the output of the primary data coder 231. FIG. 4gives, in greater detail, a possible embodiment of this dual-inputcommand reading system 220.

The first input e₁ of the command reading system 220 receives theprogram signal having undergone no processing and hence no attack apartfrom the reading from its storage medium 180. It is coupled to awatermark reading device 221 (known as a watermark reader). Since theyhave undergone hardly any processing, the secondary data are hardlyaffected by noise and their reading is more reliable. However, thetriggering commands thus obtained are no longer synchronized with theimage or the image sequence (sound, video, etc.) in which the secondarydata from which they emanate was watermarked. This is all the more sowhen the primary data undergo, furthermore, at least one additionalprocessing by virtue of the coder 231. This is why, a synchronizationdevice 225 receives the triggering commands read by the watermarkreading device 221. This synchronization device 225 is coupled to thesecond input e₂ of the command reading system 220. On this input, itreceives data on the basis of which it is capable of calculating thedelay of the commands for triggering of the secondary data with regardto the primary data so as to transform these triggering commands so thatthey are synchronized with the primary data.

In the example given in FIG. 3, this second input e₂ of the commandreading system 220 is coupled to the output of the primary data coder231. Thus, the synchronization device 225 takes account of the delayinduced by the coding performed by the device 231 on the primary data.

The watermark reading device 221 is coupled directly with the output ofthe program signal reading device 211 since the watermarks are generallyvery sensitive to attacks, in particular to those induced by the coderssuch as the primary data coder 231. However, if the watermarkingtechnique is sufficiently resistant (error rate less than a giventhreshold) to attacks of the broadcasting channel for the primary data211-231, the watermark reading device 220 can be coupled in parallelwith the input of the primary data in the multiplexer 240. In this case,according to the format of the signals transmitted to the decoders ofthe end user (middleware), the synchronization device would not benecessary since the triggering commands obtained by the watermarkreading device would be synchronized.

Specifically, various formats of signals transmitted to the end user'sdecoders exist. The oldest formats are for property formants: OpenTV,MediaHighway, etc. The most recent: MHP is the DVB standard.

This latter format: MHP, employs an image-wise synchronization means.Through a message transmitted by the interactive applicationbroadcasting device 235, for example CORAL (Thales Broadcast &Multimedia product) to the end user's decoder, the application knows thetime base of the program. Thus the triggering commands comprise theinstant in this time base of triggering of the broadcasting or of theactivation of the interactive application. This instant corresponds tothe instant in this same time base of the image formed by the primarydata in which the secondary data forming this triggering command werewatermarked.

FIG. 5 a is a representation of the progress of an image and of theassociated interactive application in the broadcasting channel accordingto the invention, corresponding to the use of an interactive systemhaving the synchronization possibilities of the MHP standard. The firstbold curve s₂₁₁ represents the program signal at the output of thereading device 211. This reading begins at the instant to and terminatesat the instant t_(n). The image I₀ read at the instant to is the firstimage of the sequence. It is identified by secondary data transporting asynchronization message. The image I₁ is read at the instant t₁. Theinstants t are expressed in a universal time base b_(u). This sameprogram signal after coding by the coder 231 has undergone a certaindelay as is represented in the second bold curve s₂₃₁. It begins at theinstant T₀ and terminates at the instant T_(n). These instants T aregiven in the time base specific to the program consisting of the primarydata to which the interactive applications in question pertain. Theimage I₁* which corresponds to the coded image I₁ is provided at theinstant T₁* by the coder 231. The third curve s₂₂₁ shows the instant t₀′at which the synchronization datum associated with the first image I₀ ofthe sequence is read, and the instant t₁′ at which the secondary datumwatermarked in the primary data of the image I₁ by the watermark readingdevice 221 is read. The last line gives the set in a universal time basethe instants related to image I₁: the instant t₁ of reading of I₁, theinstant t₁* of output of obtaining the coded image I₁*, the instant t₁′of reading of the watermarked data in I₁.

Thus the triggering command, for example for activating the interactiveapplication identified by the secondary datum watermarked in the imageI₁, comprises not only the identifier of the interactive application tobe activated, the code commanding the end user's decoder activationthereof, but also the instant at which it must be activated. Thisinstant must be equal to T₁*, corresponding to the image I1 expressed inthe time base of the program, with T₁*=T₀+(t₁′−t₀′). The reading device220 receiving the signal s211 on its input e1 and the signal s231 on itsinput e2 can easily calculate (t₁′−t₀′), that is to say the gap betweenthe instants of reading of the secondary data associated respectivelywith the images I₀ and I₁. It can moreover sample the value T₀ of thetime base of the program present on e2 at the moment at which ittransports the image I₀, still characterized by the secondarysynchronization data. Once the value of T₁* has been calculated, thereading device immediately dispatches an activation command to thebroadcasting device 235, before the instant of broadcasting of the imageI*₁ (generally the reading time of the device 220 is much less than thecoding time of the device 231).

Certain interactive systems, in particular OpenTV or MediaHighway do notemploy activation commands that make reference to the time base of theprimary data. Moreover, the decoder of the end user receiving signals ofthis type generally activates the interactive application as soon as thelast packet comprising the interactive application is received.Specifically, the interactive application is segmented and transmittedin packets by way of the multiplexer 240, of the modulator 250 and ofthe antenna 260.

FIG. 5 b is a representation of the progress of an image and of theassociated interactive application in the broadcasting channel accordingto the invention, corresponding to the broadcasting signals of OpenTV orMediaHighway type. The first bold curve s₂₁₁ represents the programsignal at the output of the reading device 211. This reading begins atthe instant t₀ and terminates at the instant t_(n). The image I₀ read atthe instant t₀ is the first image of the sequence and is identified bysecondary data transporting a synchronization message. The image I₁ isread at the instant t₁. The instants t are expressed in a universal timebase b_(u). This same program signal after coding by the coder 231 hasundergone a certain delay as is represented in the second bold curves₂₃₁. The image I₁* which corresponds to the coded image I₁ is providedat the instant t₁* by the coder 231. The third curve s₂₁₁ shows theinstant t₀′ at which the synchronization datum associated with the firstimage I₀ of the sequence is read, and the instant t₁′ at which thesecondary datum watermarked in the primary data of the image I₁ by thewatermark reading device 211 is read.

The fourth line gives the set in a universal time base the instantsrelated to the image I₁: the instant t, of reading of I₁, the instantt₁* of output of obtaining of the coded image I₁*, the instant t₁′ ofreading of the watermarked data in I₁.

To synchronize the triggering of the activation of the interactiveapplication with the reproduction of the image in which the secondarydata comprising this triggering command are watermarked, it isconceivable for the synchronization device 225 to give the order to theinteractive applications broadcasting device 235 to transmit to themultiplexer 240 the interactive application's last packet identified A₁at the instant at which the coder 231 transmits said image I₁* to themultiplexer 240 as shown by the last curve s₂₃₅. In particular tocommence, the synchronization device 225 calculates the relative delayt₀*′−t₀′ induced by the coder 231. To do this, the synchronizationdevice 225 can comprise a watermark reading device that profits from thea priori knowledge of the secondary data that it seeks to read from theprimary data at the output of the coder 231. Thereafter, during thereading at t₁′ of the secondary data related to I₁, the reading device221 knows when to despatch, via the module 225, a command forbroadcasting the last packet of the application to the device 235,taking account of the delay time introduced by 231 and knowing its owntime required to read the secondary information.

This example of synchronization of the secondary data with the primarydata can also be applied to the MHP standard.

Other types of command reading system 220 may be envisaged having thesame command function for controlling the interactive applicationbroadcasting device 235. In general, the triggering commands emanatingfrom the command reading system 220 are synchronized with the images inwhich the secondary data comprising these triggering commands arewatermarked. The command reading system 220 may comprise one or moreinputs. It receives the program signal with the primary data and thewatermarked secondary data that has or has not undergone one or moreprocessings. It furthermore receives the information necessary forperforming the synchronizing, this information possibly being obtainedfrom the abovementioned program signal.

The production and broadcasting channels described may be used not onlyfor secondary data comprising interactive commands for applicationtriggering but more generally for any type of secondary data. The use ofsecondary data watermarked in the primary data of the program may, inparticular, allow program producers to transmit all types of commands tobroadcasting systems, not only the commands for triggering interactiveapplications as was described previously but also various commands, forexample meta data. As shown by FIG. 6, these meta data may, inparticular, consist either of information, dubbed broadcastingapplication triggering commands in what follows, related to the actualbroadcasting of the video program (number of broadcasts permitted,period of validity, broadcasting criterion (quality of the coding, etc),or information describing the program for the automatic generation of aprogram guide (EPG).

The production channel remains similar to that proposed by FIG. 2. Thepredetermined control criteria are then, for example, a function makingit possible to determine the quality of coding as a function of one ormore parameters of the primary data. In the broadcasting channel, thecommand reading system 220 may be coupled either to the interactiveapplication broadcasting device 235 as described previously, or to theelectronic program guide generator 233, or to the primary data coder231, or to the multiplexer 240, etc as shown diagrammatically by FIG. 6(this list given by way of example is nonlimiting). The command readingsystem 220 may whether or not the application triggering commands do ordo not so require be synchronized with the primary data in which theyare watermarked.

Moreover, the possibility of identifying the broadcasting channel forwhich the secondary data are destined, by virtue of an identifier of thebroadcaster contained in these secondary data, makes it possible toenvisage broadcasting applications commands, that is to say programbroadcasting conditions, that are different for each broadcastingchannel. Thus, the quality of coding desired may be different dependingon the broadcasting channel.

The invention can be implemented for any recorded program having apassive main content and one or more interactive applications be itvideo, audio, etc intended to be broadcast in respect of television,radio, networks for cinemas or auditoria, etc. The interactive programis thus obtained for lower than existing costs. It is made attractivefor the public in particular since no specific procedure needs to beperformed (telephone, use of a computer keyboard, etc). It may createprofit for the producer and/or the broadcaster. Specifically, once thissystem is available, it becomes very easy for producers of content andbroadcasters to enhance audiovisual programs, by virtue of interactiveapplications that are very simple to create and are sources of directrevenues (via a commission on the telephone communications generated) orindirect revenues (via pre-purchase trialing of consumer products, etc).

1. A broadcasting program signal, comprising: primary data for thereproduction of the passive main content of the program, wherein itcomprises secondary data watermarked in the primary data not alteringthe reproduction of the main content of the primary data, and secondarydata comprise the commands for triggering at least one applicationrelated to the main content of the primary data.
 2. The broadcastingprogram signal as claimed in claim 1, wherein said applicationtriggering commands are commands for controlling one or morebroadcasting parameters of said program signal and/or of one or moreapplications related to said program signal.
 3. The broadcasting programsignal as claimed in claim 2, wherein said broadcasting parameters ofsaid program signal are the number of authorized broadcast and/or theperiod of validity and/or the desired quality of coding of said programsignal.
 4. The broadcasting program signal as claimed in claim 3,wherein said broadcasting parameters of one or more applications relatedto said program signal are a descriptor of said program for tilecompilation of an electronic program guide.
 5. The broadcasting programsignal as claimed in claim 1, wherein said application triggeringcommands are commands for triggering the broadcasting and/or tileactivation of at least one interactive application related to the maincontent of the primary data.
 6. The broadcasting program signal asclaimed in claim 5, wherein a triggering command comprises: anidentifier of the interactive application relevant to this triggeringcommand and a code giving the type of triggering to be performed.
 7. Thebroadcasting program signal as claimed in claim 6, wherein the type oftriggering code makes it possible to determine whether it is necessaryto start or stop the broadcast and/or activate the identifiedapplication.
 8. The broadcasting program signal as claimed in claim 1,where a triggering command comprises a code for identifying thebroadcasting channel for which said command is designated.
 9. A systemfor writing commands writing secondary data, allowing the triggering ofat least one application, in a program signal comprising at leastprimary data for the reproduction of the passive main content of theprogram comprising: a first input e₁ receiving primary data for thereproduction of the passive main content of the program; a watermarkingdevice receiving the primary data of the first input e₁ and secondarydata, and generating a program signal comprising the primary data andthe secondary data watermarked in the primary data, said watermarkingnot altering the reproduction of the main content of the primary data;an output coupled to the output of the watermarking device; a secondinput e₂ receiving predetermined control criteria, a reproduction andediting device coupled to the first and second inputs e₁ and e₂, saiddevice reproducing the main content of the primary data, which contentis received on the first input e₁, and editing on its output at leastone secondary datum making it possible to control the triggering of atleast one application related to the main content of the primary data,which application is reproduced according to the predetermined controlcriteria received on this second input e₂.
 10. The command writingsystem as claimed in claim 9, wherein the predetermined control criteriaare predetermined interactivity criteria, said reproduction and editingdevice edits on its output at least one secondary datum making itpossible to control the triggering of the broadcasting and/or of theactivation of at least one interactive application related to the maincontent of the primary data, which application is reproduced at thisinstant according to said predetermined interactivity criteria receivedon this second input e₂.
 11. The command writing system as claimed inclaim 9, wherein tho program signal generated by said watermarkingdevice is a program signal as claimed in claim.
 12. A production channelcomprising in series a system for producing a program signal comprisingprimary data for the reproduction of the passive main content of theprogram and a command writing system as claimed in claim
 10. 13. Asystem for reading a command in a program signal comprising primary datafor the reproduction of the passive main content of the program and atleast one secondary datum watermarked in the primary data comprising: afirst input receiving the program signal, a watermark reading device,reading the secondary data watermarked in the primary data, thesecondary data comprises commands for triggering at least oneapplication related to the main content of the primary data, and in thatsaid command reading system comprises an output receiving saidapplication triggering commands.
 14. The command reading system asclaimed claim 15, wherein the program signal received on its first inputis a program signal as claimed in any one of claim.
 15. The commandreading system as claimed in claim 13, wherein: the secondary datacomprises commands for triggering the broadcasting and/or the activationof at least one interactive application related to the main content ofthe primary data, and said command reading system comprises an outputreceiving triggering commands synchronized such that the activationand/or the broadcasting of the interactive applications identified bythe triggering commands is synchronized with the reproduction of theprimary data in which the secondary data associated with thesetriggering commands are watermarked.
 16. The command reading system asclaimed in claim 15, which system comprises a synchronization devicereceiving at least the secondary data and generating synchronizedtriggering commands.
 17. A program broadcasting channel comprisingseveral devices, comprising: a device for reading a program signalcomprising primary data for the reproduction of the passive main contentof the program and at least one secondary datum watermarked in theprimary data, a program signal coder coupled to the output of saidprogram signal reading device, and/or an interactive applicationsserver, a device for broadcasting interactive applications coupled tosaid interactive applications server, a multiplexer coupled at least tothe output of the program signal coder and/or to the interactiveapplications broadcasting device, a command reading system coupled tothe output of said program signal reading device and/or to the output ofsaid program signal coder, a coupling of said command reading systemwith at least any one of the devices of said broadcasting channel, thetriggering commands generated by the command reading system controllingsaid device of said broadcasting channel, which device is coupled tosaid command reading system.
 18. The program broadcasting channel asclaimed in claim 17, wherein said command reading system is coupled tosaid interactive applications broadcasting device, the triggeringcommands generated by the command reading system controlling thetransmission of the interactive applications originating from saidinteractive applications server to the multiplexer and/or thetransmission to the multiplexer of the order for activation of one ormore interactive applications identified by these triggering commands.19. The program broadcasting channel as claimed in claim 18, wherein thesynchronized triggering command for activating the interactiveapplication identified generated by the synchronization device controlsthe transmission by the interactive applications broadcasting device ofthe last packet of the interactive application identified to themultiplexer triggering the activation of this interactive application.20. The program broadcasting channel as claimed in claim 18, wherein thesynchronized triggering command for activating the interactiveapplication identified generated by the synchronization device comprisesthe instant of triggering of the activation of the interactiveapplication identified in the time base of the program, this instantcorresponding to the instant of broadcasting the primary data in whichthe secondary data associated with this triggering command arewatermarked.
 21. The broadcasting program signal as claimed in claim 2,wherein said application triggering commands are commands for triggeringthe broadcasting and/or the activation of at least one interactiveapplication related to the main content of the primary data.
 22. Thecommand writing system as claimed in claim 10, wherein the programsignal generated by said watermarking device is a program signal asclaimed in claim
 1. 23. The command reading system as claimed in claim14, wherein: the secondary data comprises commands for triggering thebroadcasting and/or the activation of at least one interactiveapplication related to the main content of the primary data, and saidcommand reading system comprises an output receiving triggering commandssynchronized such that the activation and/or the broadcasting of theinteractive applications identified by the triggering commands issynchronized with the reproduction of the primary data in which thesecondary data associated with these triggering commands arewatermarked.